Redjac

Redjac was a malevolent non-corporeal entity that was responsible for numerous murders of women across many worlds throughout the centuries, feeding on the fear generated by its victims upon their death.

Nearly a century later, in 2370, the USS Enterprise-D was dispatched to Enoch-7, where Redjac had instigated an outbreak of violence which threatened to erupt into nuclear war. Once the ship had arrived, Redjac took possession of the vessel's holodeck, where it discovered Data's Sherlock Holmes program. Through this, it was able to re-enact its old persona of Jack the Ripper, and trapped the crew in 19th century London. Redjac then challenged the android to save them while it attempted to murder them, such as nearly killing Counsellor Deanna Troi in a waterside dock and using its powers to force Worf to a more feral mentality before Captain Jean-Luc Picard managed to talk Worf down. The crew was ultimately able to trick Redjac into focusing all of its energy into one spot as it battled Worf, where it became trapped inside a photon torpedo. The torpedo was launched and left abandoned on a nearby moon, leaving Redjac trapped. (TNGcomic: "Embrace the Wolf")